Any way to sort a list of forums by activity?

[BrandonC]

I'm going to have a large number of forums for music artists/groups, and I'd like to be able to sort them by activity. Here's what the layout witll look like:

Artists
--A
----A Perfect Circle
----AFI
----Aerosmith
----Amos, Tori
----etc.
--B
----Barenaked Ladies
----Britney Spears
----etc.
--C
----Chemical Brothers
----Coldplay
----etc.

There will be threads in all of the individual artist forums that users create. I would like to be able to sort the forum list itself by activity....so that when someone posts in the Britney Spears forum, it will pop it up to the top of the list that you see when you click on "B" in the Artists category. Just like the way the threads inside a forum behave, except that it's with sub-forums within a forum.

Is there ANY way to do this, or am I SOL?

thanks....